The Swedish Nuclear Bomber: SAAB A36

[LostCosmonaut]

I was originally going to post this in the J35 thread (since that's turned into the general Swedish aviation thread), but I felt that it'd get more visibility here.

 

SAAB A36

 

(via http://forum.valka.cz/topic/view/55568/SAAB-A-36)

 

During the 1950s, many nations sought to develop nuclear weapons. One of these was Sweden, who hoped that nuclear weapons could help maintain their neutrality during the Cold War. However, when developing nuclear weapons, a delivery system is also needed. For Sweden, that would have been the A 36, a dedicated nuclear strike aircraft and one of the "missing pieces" in the Swedish aircraft sequence (between the 35 and 37).

 

Development of the A 36 began in 1952, as part of SAAB's 1300 series of projects (which included numerous other designs). The requirements for a Swedish nuclear strike aircraft were different from those of other major countries. The most likely opponent (the USSR) was less than 500 kilometers away across the Baltic, while American bombers would have to fly more than ten times as far to reach their targets. This was evident in designs such as the B-36 and B-52, which had very large wingspans and fuel capacities, as well as large payloads. Additionally, a Swedish nuclear bomber would have to be capable of operating from dispersed airfields, in accordance with Swedish doctrine. Obviously, the Swedish nuclear bomber would end up looking quite different from its American or Soviet counterparts.

 

Numerous SAAB engineers were involved with the A36 development (quite an undertaking, as the company was developing the J35 at the same time while also producing the J32). Among them was Aarne Lakomaa, a transplanted Finn who had gained fame for developing the Morko-Morane fighter during the Continuation War.

 

From the start, the Swedish bomber (at this point it had yet to be designated A 36) was designed for high speed. Numerous configurations were studied, with swept wings or delta wings on various designs. Top speed was planned to be around Mach 2, which would have made the A36 almost as fast the J35.

 

SAAB 1323 (or 1300-23), an early step in the A36 development.

 

 

SAAB 1371 (1300-71), a proposal which made it as far as wind tunnel testing.

 

As can be seen from the previous drawings, many of the designs were planned to have two engines. As with other Swedish aircraft of the time, the A36 was planned to use license built British engines. Among the engines considered were the de Havilland Gyron and smaller Gyron junior. However, at some time early in the development of the program, it was decided that the aircraft would be powered by the Bristol Olympus turbojet, the same engine that powered the British Vulcan bomber. However, for use in a supersonic aircraft, it would have required modification, such as the fitting of an afterburner, and a new intake. (The Olympus was eventually developed for use in supersonic aircraft, such as the TSR-2 and Concorde.) With such a large and powerful engine, it became apparent that only a single engine would be needed in the A36.

 

At such high speeds, the A36 would have experienced significant aerodynamic heating. This concerned Swedish engineers, who were afraid that the heat would damage contemporary nuclear weapons (or even lead to them detonating prematurely). As a result, it was decided that the payload would be carried within an internal weapons bay. This would reduce drag, improving performance, but it would also limit payload, while decreasing the internal volume available for fuel, avionics, and other systems. By the time the A36 design had progressed  to the 1376 and 1377 configurations, payload was determined to be a single 800 kilogram nuclear weapon, carried internally. This is roughly comparable in size to the American Mark 7 bomb, deployed tactically around the same time. As far as I know, no provision was ever made for the A36 to have air-to-air capabilities.

 

By 1957, the design of the A36 (which had by now received a formal Swedish Air Force designation) was almost finalized.

 

(SAAB 1376, with chin intake)

 

(Drawing of SAAB 1377 with dorsal intake, similar to YF-107)

 

Most documents show the 1376 as the chosen design. 1376 was a moderately sized aircraft, somewhat smaller than the American F-105 (which had a similar role to the A36). The wing was a conventional delta with 62 degree sweep, which would have given good performance in the supersonic regime. I am uncertain whether the A36 would have utilized a variable geometry inlet. A fixed inlet would have had to be optimized for a certain speed; this would mean that the A36 would have been inefficient at low Mach numbers, or been had it speed limited by the inlet design. (Read more about inlet design here).

 

 

Although work on the A36 was progressing well, by 1957 it was apparent that Sweden could not afford to develop the A36, nuclear weapons, and other vital defense programs. As the A36 would have been relatively lacking in conventional capability, it was decided to cancel the program. (Ultimately, the nuclear weapons program would be shut down during the 1960s as well). Some of the money saved was used to develop the A37 Viggen, which proved to be a competent multirole aircraft during the 1970s and beyond. Ultimately, while it would have been interesting from a technological standpoint to see the A36 fly, its cancellation was probably the right choice.

 

I have not found any documents showing that the A36 was ever given a name (such as 'Draken' for the J35). Occasionally references can be found to the A36 'Vargen' (Wolf) online, but it appears that these are the inventions of either modeling companies or someone with an overactive imagination.

 

A36 (1376 design) specifications (approximate):

Length: 17m

Wingspan: 9.6m

Height: 2.5m

Wing Area: 54m²

Empty Weight: 9000 kg

Max Weight: 15000 kg

Wing Loading at Max Weight: 280 kg/m²

Payload: 800 kg

Max Speed: Mach 2.1

Ceiling: 18000m

Combat Radius: 410km (?)

Crew: 1

Engine: 1x Bristol Olympus Turbojet

 

 

 

 

 

Sources:

http://u-fr.blogspot.com.br/2010/12/cancelled-saab-aircraft-projects.html

http://www.secretprojects.co.uk/forum/index.php/topic,683.0.html

http://forum.valka.cz/topic/view/55568/SAAB-A-36

[Belesarius]

Interesting read. Thanks Lost!

[LostCosmonaut]

Made a few edits, fixed a grammatical error and added a bit more info.